A visual evoked potential (VEP) is also called as a visual evoked reaction, which is an electrical reaction of an visual center of an occipital lobe recorded in the dermal surface of the head when the retina is stimulated by flashing or an image and then the signal is delivered along an optic pathway. It mainly reflects a transfer function from a ganglion cell of the retina to the visual cortex. The 17th region of the visual cortex in the cerebral cortex mainly receives projection of nerve fibers within 10 degree in the central retina 100, and the projection region is nearest to the scalp surface, so most of information about the VEP is originated from macula lutea region. The VEP not only reflects a function of a visual cortex of the occipital lobe, but also reflect a function of a transfer channel from the macula lutea region of the retina and a ganglion cell of the macula lutea region to the visual cortex. VEP is an important method for objectively evaluating and inspecting the visual nerve function (cf. Yingfu PAN, Clinical evoked potential, Edition 2, People's medical publishing house).
The Visual evoked potential is an electrical reaction of the occipital lobe of the cerebral cortex on the visual stimulation and represents a potential change caused by the stimulation received by the retina and conducted to the cortex of the occipital lobe through the visual pathway. As can be seen from a mechanism for generating the visual evoked potential, no matter which of the visual evoked potential, it is the most import that the retina receives visual stimulation and the stimulation on the retina has to be projected through the dioptric system of the human's eyes. Thus, the quality of an optical system of the human's eyes will directly affect the quality of the stimulation projected onto the retina. For the transfer of the visual stimulation to the retina, except for diffraction generated by the pupil of the human's eyes which is incapable of being avoiding, the optical aberration is the most important influential factor. It is well known for the people that the optical system of the human's eyes is not an ideal optical system. Except for the low-order aberrations such as defocus and astigmatism, there are many high order aberrations having more complex shape (e.g. spherical aberration, trefoil aberration and so on). Furthermore, the aberration of the human's eyes is not stationary and dynamically varies with time (D. R. Williams, & Hofer, H. Formation and Acquisition of the Retinal Image. In: J. S. W. Leo M. Chalupa (Ed.), The Visual Neurosciences, the MIT Press, Cambridge, Mass., London, England, 2003). The existing VEP inspection only corrects the low order aberration of human's eyes by ametropia compensation of the lens, and a correction lens with a high degree of separation can't accurately compensate the low order aberration. The existence of the residual low order aberration and the high order aberration of the human's eyes less affect the VEP inspection at a lower spatial frequency. However, when an image with a higher spatial frequency is utilized to stimulate for the VEP inspection, and an abnormal phenomenon is found, it can't be determined wither there is abnormal for the visual pathway and perhaps it is caused by the optical aberration of the testee which is not corrected (“Electrophysiological research on the effects of optical-induced ametropia on transfer of visual signal and response of visual signals in the visual cortex”, Master degree thesis of Laiqing Xie, Tianjin Medical University, 2009). Therefore, when the VEP is utilized to evaluate the visual nerve function and to objectively inspect eyesight of human's eyes, the influence of the human's eyes aberration on the projection of the visual stimulation to the retina within the eye ground has to be eliminated so as to obtain an accurate result for the VEP inspection.